Conventionally, various types of a conveyor line system, which is configured to convey a conveying product to which a thermoreversible recording medium serving as a recording part is attached to the predetermined conveying direction, and irradiate the thermoreversible recording medium with laser light to rewrite an image, have been proposed (see, for example, PTLs 1, 2, and 3).
The conveyor line system is equipped with an image erasing device configured to irradiate a thermoreversible recording medium, to which an image has been recorded, with laser light to erase the image, and an image recording device configured to irradiate the thermoreversible recording medium, from which the image has been erased by the image erasing device, with laser light to record a new image. Note that, the image erasing device and the image recording device may be collectively referred as an image processing device.
It is desired that laser light is accurately applied only to a thermoreversible recording medium, when an image is recorded, or the formed image is erased by irradiating the thermoreversible recording medium with the laser light. In the conveyor line system, however, laser light may be repeatedly applied to, not only the thermoreversible recording medium, but also an area of a conveying container, which surrounds the thermoreversible recording medium. If laser light is repeatedly applied to the conveying container as described above, a surface of the conveying container may be scraped as illustrated in FIG. 1B depending on a constitutional material or structure of the conveying container, because the conveying container absorbs the laser light. FIG. 1A is a photograph depicting a surface of a conveying container formed of a black polypropylene (PP) resin plate before laser light is applied, and FIG. 1B is a photograph depicting the surface of the conveying container formed of a black polypropylene (PP) resin plate after irradiated with laser light 10 times. Note that, a surface texture of the area irradiated with the laser light depicted in FIG. 1B was rough, as it was touched with a finger.
This is not a problem if the conveying container is disposal. However, the conveying container to which the thermoreversible recording medium serving as a recording part is attached is typically used repeatedly. Therefore, a surface of the conveying container is scratched, or scraped, as the material of the surface of the conveying container is melted or sublimated by repetitive use of the conveying container and irradiation of laser light. Moreover, there is a problem that the durability of the conveying container is low, as the surface of the conveying container is scraped.
Even when irradiation of laser light is performed on a surface of a conveying container only once, for example, confidential information is recorded on the surface of the conveying container depending on a relationship between absorbance of the recording part and the absorbance of the conveying container. Therefore, there is a problem of leakage of confidential information.
Two cases are considered whey the conveying container is irradiated with laser light.
The first case is a case where a thermoreversible recording medium is not attached to a position where laser light is applied, for example, as the thermoreversible recording medium attached to the conveying container is pealed, a conveying container, to which a thermoreversible recording medium is not attached, is mixed in the line by accident, or a direction of the conveying container is mistaken by a worker for putting the conveying container in the line.
The second case is a case where a position of the thermoreversible recording medium and a position where laser light is irradiated are mismatched, for example, as a position of the conveying container placed on the conveyor line is misregistered, or the thermoreversible recording medium attached to the conveying container is shifted from an appropriate position, or a position where the thermoreversible recording medium is stopped is misregistered because the conveying container conveyed at high speed go beyond the stopper due to excessive force, or the conveying container is bumped into the stopper with excessive speed to move back in the opposite direction to the conveying direction due to the reflection from the impact with the stopper, or there is an error in positioning information when the conveying containers of several sizes to which the thermoreversible recording media is attached to the different positions are conveyed, against the intention that the laser light irradiation position is changed per conveying container, or a shape of the conveying container is changed as it is repetitively used.
A rate of the misregistration caused due to the aforementioned two cases changes depending on a performance of the conveyor line for use, or the conveying container for use, but it is 10 or less relative to 100 conveying containers. It is considered based on the above that laser light applied to rewrite an image on the thermoreversible recording medium attached to one conveying container is applied to the conveying container at the maximum rate of 1/10 relative to the number of the processing repeated.
Meanwhile, it is desired to record as much information as possible to a thermoreversible recording medium. If the information is recorded on the entire surface of the thermoreversible recording medium to this end, the information is recorded to the edges of the thermoreversible recording medium, and thus a probability that laser light is applied also to the conveying container becomes high, as the misregistration occurs. In the case the image on the thermoreversible recording medium is erased, similarly, laser light is applied to the entire surface of the thermoreversible recording medium to erase the information recorded on the entire surface of the thermoreversible recording medium. If the misregistration occurs, therefore, laser light applied to erase the information of the edges of the thermoreversible recording medium is also applied to the conveying container.
Recently, a high throughput has been desired for a conveyor line system. To this end, a conveying speed of a conveying container needs to be set as fast as possible. Therefore, a conveying container is bumped into a stopper with a force, a misregistration becomes significant. In this case, a problem that laser light is applied to conveying container tends to occur.
As for a method for solving the aforementioned problem, for example, disclosed is a method where a sensor for detecting a thermoreversible recording medium is provided above a conveyor line, and laser light is not emitted at equal to or above the predetermined power when a thermoreversible recording medium is not detected (see PTL 4). This method can prevent a conveying container from being irradiated with light when a thermoreversible recording medium is not attached to a position where laser light is applied. However, there is a case where a position where a thermoreversible recording medium is attached and a position where laser light is applied are misregistered. Therefore, problems that a conveying container is scratched or scraped, and durability thereof is degraded by irradiating the conveying container with laser light have not yet solved.